The legibility of letters and words

The saying made famous by Matthew Carter that "type is a beautiful group of letters, not a group of beautiful letters”, highlights the fact that although a typeface consists of a number of letters it is when the letters are assembled in a word that they become type. However, research indicates that what makes letters legible in isolation is not necessarily the same as what makes them legible in words. Is it possible to create a typeface where both letters and words have a high level of legibility or are those factors so different that they cannot be combined? Through a literature review on relevant experimental investigations, I will in this talk present examples of when the legibility findings on letters and words correlate and when they differ.